Resize PDF Pages

Resize PDF Pages gives every page of a PDF the same paper size. It is for reprinting a mixed-size document on one paper stock (a report with A4 text pages and a fold-out A3 chart), for shrinking an oversized scan to Letter, or for fixing a download that came out an odd size. The file is changed in your browser and never uploaded.

There are two ways to do it, and they behave differently.

Fit scales each page's content down or up so the whole page — including its existing margins — sits inside the new paper, then centres it. This is the mode that stops anything being cut off, and it is what you want when a page is wider or taller than the paper you are printing on. The cost is honest and visible: because the content is scaled, text and line weights are shrunk or enlarged with it. A Letter page fitted onto A4 comes out at about 95% (see the worked examples), which is a slight reduction; a large plan fitted onto A4 can become very small.

Keep changes only the paper box: the page becomes the size you choose, but the content is left exactly where it was, at its own size, anchored to the page's bottom-left corner. Nothing is scaled. If the new paper is bigger, the extra space shows as margins along the top and right edges; if it is smaller, whatever now falls outside the page is clipped when displayed and printed. Keep is the right choice when you do not want text re-sized at all and you can accept white space or clipping.

A page's own rotation is respected. If a page is displayed landscape because it carries a 90° rotation setting, the new paper box is written the other way round, so the page still shows up the way the file says it should and still ends up at the size you chose — not sideways. The rotation itself is not changed.

The sizes A4, A3 and A5 are the ISO 216 trimmed sizes, which are defined in millimetres (A4 is exactly 210 × 297 mm); Letter and Legal are the US sizes defined in inches (8.5 × 11 and 8.5 × 14 in, which is 215.9 × 279.4 and 215.9 × 355.6 mm). A custom size can be typed in millimetres or inches, and is converted to PDF points (1/72 inch) exactly.

The PDF is not re-rendered, so nothing is rasterised: the scale and the shift are added around each page's existing content as a graphics-state transform, meaning text stays vector, selectable and searchable, and images keep every pixel. The whole file is re-saved, so its internal layout and size can differ from the original, and a digital signature will no longer validate, because it covers the exact bytes of the untouched file. Password-protected and permission-locked PDFs are refused with a clear message; files up to 200 MB are accepted.

Everything runs in your browser with pdf-lib. You can confirm in your browser's developer tools, on the Network tab, that no request carries your document — the site loads its own scripts and analytics, but never your file.

1. The file's first bytes are checked for the PDF signature, and pdf-lib opens it; encrypted or damaged files are refused with a message that names the file. 2. The chosen size becomes a width and height in points. An ISO 216 or US preset is converted from millimetres or inches: width_pt = width_mm ÷ 25.4 × 72, and height_pt = height_inch × 72 (so A4 = 595.2756 × 841.8898 pt, Letter = 612 × 792 pt). A custom size must be greater than 0 and come out between 36 pt (0.5 in) and 14,400 pt (200 in). 3. Each page's current MediaBox (its paper box) and its /Rotate are read. For a page turned a quarter turn (Rotate 90 or 270) the target box has its width and height swapped, so the page still displays at the chosen size. 4. In fit mode the scale is the tighter of the two ratios: scale = min(target_width ÷ page_width, target_height ÷ page_height). The content is scaled by that factor, the page box is set to the target, and the content is shifted so it is centred: translate_x = (target_width − page_width × scale) ÷ 2, and the same for y. 5. In keep mode no scale and no shift are applied — only the page box is set. 6. The document is saved and offered as <name>-<size>.pdf (for example report-a4.pdf or poster-300x400mm.pdf).